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Energy Metabolism, insulin, Diabetes
Solomon 4/13/11 lecture 2 hrs Guyton ch 70,78 (part of 67-69)
42
Physiology
Undergraduate 4
03/21/2011

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Term
carbs, fat, amino acids
Definition
what are the 3 sources of energy for the body?
Term
1) maintaining body temp
2)muscle contraction
3) biosynthesis
4) cell transport
5) growth
Definition
how is energy expended by the body?
Term
1)ATP generation
2) storage as glycogen
3) biotransformation (lipid deposition)
Definition
what are the 3 ways glucose is used by the body?
Term
1)biosynthesis of peptides, and proteins
2)gluconeogenesis
Definition
what are amino acids used for?
Term
1)energy storage
2)energy generation(beta oxidation)
4)gluconeogenesis
Definition
how is fat utilized in the body?
Term
14g
Definition
how many grams of islet cells are in the body?
Term
alpha
beta = most prevalent 50-60%
delta
Definition
what are the 3 major cell types in islets of langerhans? which is most prevalent?
Term
alpha: synthesize and secrete glucagon (increase glucagon and blood sugar)

beta: synth & secrete insulin (increase insulin to decrease blood sugar)

delta: synth & secrete somatostatin
(somatostatin inhibits alph and beta cells)
Definition
what do alpha cells do? beta? delta?
Term
1)increase in glu
2)increase in FA and amino acids
3) incretins (GIP)
Definition
what causes an increase in insulin secretion?
Term
1)increases glu transport into cells
2)stimulates a.a. uptake into cells
Definition
what does insulin do within a matter of seconds?
Term
increases activity of metabolic enzymes inside of cells
Definition
what are the actions of insulin within a few minutes?
Term
1) increases protein formation and prevents protein degradation
2) promotes growth(with help of growth hormone)
Definition
what are the effects of insulin within hours to days?
Term
1)glucose enters a beta cell or hepatocyte via facilitated diffusion down its concentration gradient (GLUT-2 transporter)
2) glucose is converted to glucose-6-phosphate via glucokinase (this prevents the molecule from leaving the house because it is impermeable to the membrane)
3) G6P is oxidized creating ATP which closes ATP sensitive K+ channels
Definition
describe how glucose enters a (beta) cell (the cellular mechanisms)
Term
1) K+ channels closing causes the membrane to depolarize and open calcium channels
2) calcium enters and helps the insulin out somehow
Definition
Once ATP sensitive K+ channels close, what happens to the beta cell to cause insulin secretion?
Term
aa: augment effect of glucose
FA: augment effect of glucose, may be toxic
hormones: growth hormone stimulates secretion, and cortisol is secreted by tumors

(something to do with gigantism and acromegaly)
Definition
how do amino acids, fatty acids, and hormones stimulate insulin secretion?
Term
Incretins, ensure similar glucose excursions regardless of the glucose load
Definition
why does the blood glucose concentration over time change about the same whether glucose is ingested in varying amounts, or orally versus intravenously?
Term
oral glucose stimulates more insulin secretion than IV glucose.

no difference really(oral SLIGHTLY higher), because incretins amplify insulin secretion so glucose excursions are kept constant
Definition
which stimulates more insulin secretion? oral intake of glucose, or intravenous intake? in the end is there a noticeable difference?
Term
70%
Definition
what percent of post-glucose insulin secretion is due to the incretin effect?
Term
after oral glucose intake, via gut hormones
Definition
where is incretin secreted?
Term
GIP and GLP-1, they both augment the effect of glucose on insulin secretion
Definition
incretins are released from the small intestine in response to glucose by enteroendocrine cells, what are the incretins? what do they do to insulin?
Term
there are structural changes and tyrosine kinase autophosphorylates, leading to a phosphorylation cascade with (IRS) insulin receptor substrates that
1) increase glucose transport(uptake), and
2) increase synthesis
Definition
what happens when insulin binds to a cell membrane?
Term
all most all tissues
especially skeletal musc, liver, and fat but NOT CNS
Definition
where does insulin induce glucose uptake? especially? not at all?
Term
insulin increases transporter production in muscle/fat

in the liver insulin tells the cells to make more glucokinase
Definition
what does insulin do to the GLUT-4 transporter in muscle and fat cells? what does insulin do in the liver mainly?
Term
1)increases glu uptake
2)increases glycogen formation
3)decreases use of glycogen for energy
Definition
what 3 things does insulin do to skeletal specifically?
Term
1) increases glu uptake
2) decreases uses of fats for energy
3) enhances synth/storage of fat
Definition
what 3 things does insulin do in adipose tissue?
Term
1)increases glu uptake
2) increases glycogen formation
3) increase FA formation (from glu)
4) decreases use of glycogen for energy
5) decreases formation of new glucose
Definition
what 5 things does insulin do to the liver?
Term
low blood glucose, or increase in blood amino acids
Definition
what stimulates glucagon secretion by alpha cells?
Term
1)increases breakdown of glycogen(glycogenolysis)
2)increases glucose production (gluconeogenesis)

-> increase blood glu levels, and increases breakdown of fat
Definition
what does glucagon do in the liver?
Term
glucagon starts taking effect
Definition
when we eat, insulin starts taking effect, what happens 2 hours later?
Term
increase in blood glucose, amino acids, and fatty acids

somatostatin decreases moth insulin and glucagon secretions because it inhibits alpha and beta cells (feedback loop)
Definition
when are delta cells stimulated to secrete? what does this do to insulin and glucagon?
Term
glucagon(panc), growth hormone(petuitary), cortisol(adrenal gland), and epi(adrenal gland) are increased

insulin(panc) is decreased
Definition
what hormones are increased to switch from carb metabolism to lipid? which decrease?
Term
1)hormone sensitive TAG lipase activated -> TAG's are hydrolyzed to GA and glycerol

2) there is a hepatic conversion of FA to phospholipids, and cholesterol

3) this can lead to ketosis or acidosis that can be toxic in a few hours because FA->acetoacetic acid-> betahydroxybutyric acid->acetone
Definition
what does insulin do in fat metabolism?
Term
polyuria, polydypsia, polyphagia
Definition
what are 3 symptoms of diabetes mellitus?
Term
1) increases blood glucose
2) carb metabolism switched off
3) fat metabolism switched on
Definition
what does diabetes do to 1) blood glucose
2) carb metabolism 3) fat metabolism
Term
juvenile (age 14) onset
complete lack of insulin due to destruction of beta cells

5-10% of diabetics
Definition
when does type 1, T1DM, or IDDM onset and what happens to insulin? what percent of diabetics does this account for?
Term
adult onset, insulin resistance (insensitivity to insulin, relative lack of insulin)

90-95% of diabetics
Definition
when does type 2, T2DM, or NIDDM onset and what happens to insulin? what percent of diabetics does this account for?
Term
1) genetic suceptibility
2) chronic autoimmune damage
3) environmental precipitation (viral infection)
Definition
what are the 3 things that are supposed causes of T1DM?
Term
1)decreased # of insulin receptors
2)toxic effects of lipid in muscle or liver
3) late loss of insulin secretory capacity
Definition
what are the possible causes of T2DM?
Term
T1DM: insulin administration
T2DM: weight loss & exercise, insulin sensitivity, decrease in hepatic glucose production, increase in insulin secretion
Definition
what is the treatment for T1DM? T2DM?
Term
1) marked hyperglycemia
2) dehydration
3) metabolic acidosis
4) coma, death
Definition
what are the acute complications of T2DM?
Term
microvascular problems: renal, retinal, neural

macrovascular: cardiovasc disease, stroke, peripheral vascular disease
Definition
what are the chronic complications of T2DM?
Term
diabetes mellitus
Definition
what causes 60% of blindness? & 1/2-1/3 of all renal problems?
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